The present invention relates to those impact sensor being incorporated, e.g. in cameras and other precision instruments or air bag in the automobile industry, which will induce current interrupting motion, whenever an impact force exceeding predetermined value would have been encountered as well as to those impact-pressure sensors which are designed to interrupt current, whenever an impact or a pressure exceeding predetermined value would have evolved at those electronic parts subject to an internal pressure, e.g. in lithium ion battery, capacitor, etc.
A plurality of rechargeable types of batteries such as lead accumulators, nickel-cadmium-batteries is incorporated in conventional electronic apparatuses, e.g. cellular phone, video-camera, etc. Those batteries are susceptible to such kind of trouble as over-chargedxe2x80x94or short-circuited state caused by failure or mishandling of electronic apparatuses, in which case over heated batteries, gas generation from decomposed electrolytic solution, elevated pressure in the batteries resulting in an explosion would be often encountered. As the result those rechargeable types of batteries are normally equipped with different types of protective device.
Japanese Laid-open Utility Model No. 64-38764 discloses e.g. a protective device which provides a flat metal collecting lead extending from electrically negative or positive metallic collector up to output terminal with a circular or elliptic perforation, around which fluoric resin is then made deposited.
Such kind of protective device is featured with a narrow portion of collecting lead localized at said perforation which would become readily disrupted, whenever an elevated pressure will evolve inside the battery. In addition the protective device is kept free from any possible misoperation due to the fact the area around the perforation is covered by fluoric resin which is sufficient to make said area adequately corrosion proof.
Japanese Laid-open Patent No. 6-36752 discloses also a protective device which provides a seal piece atop the battery with a pressure relief bore and is equipped with a thin film having a diaphragm corresponding to said bore in an area outside the seal piece. The protective device insures a stabilized tripping pressure, since the diaphragm and thin film with an uniform thickness may be accepted by the device.
In the protective device disclosed under Japanese Laid-open Utility Model No. 64-38764, however, the fluoric resin covering the area liable to be ruptured around the perforation makes it more inconvenient to adjust the tripping pressure towards the predetermined value, and to provide perforation of predetermined size within the narrow width of lead where it is required under the recent trend to make rechargeable batteries more compact. In addition, it is rather difficult to make the protective device released in a safe manner as the current collecting lead is originally designed to be ruptured mechanically, in which case a larger tripping pressure should be maintained.
In case of the protective device disclosed under Japanese Laid-open Patent No. 6-36752 it is required to equip the bore in the seal piece with both a diaphragm and a thin film resulting in a complicated configuration. This will make it more difficult to prepare the protective device under the recent trend towards a miniaturized batteries. Further it appears that a misoperation of protective device is liable to be caused by possible interference from outside resulting in an eventual discharge of electrolytic solution upon tripping, since the diaphragm is designed to remain left under an exposed state.
Originally these protective device is based on a conception to react against an elevated pressure. They are, however, by no means designed to interrupt current in such a case where batteries are subjected to an impact, intensity of which exceeds a predetermined level. To cope with such case of impact interference conventional batteries have to be equipped with another type of sensor.
The present invention aiming to solve the aforementioned disadvantage of prior art offers impact- and impact-pressure sensors which may be readily assembled and made more compact so as to be integrated into rechargeable batteries.
The impact sensor under the present invention comprises: main part of sensor having a cavity, at least one side of which is made susceptible to fracture; impact force transfer member; weight being housed in the cavity; and seal member for the cavity having the weight confined therein. Upon occurrence of interference by an impact force exceeding predetermined level a fracture will occur at the defined area at the cavity through the acceleration force caused by the weight.
The impact-pressure sensor under the present invention comprises: main part of sensor having an isolated hollow, at least one side of which is made susceptible to fracture; member provided within the fracture part designed to transfer force; seal member which is secured to the main part of sensor and is located at the predetermined position spaced apart from the fracture part; and weight being housed in the hollow. Within said seal member is provided a passage that links up said hollow with outside environment. Should an impact exceeding the predetermined level have been encountered the fracture part is apt to be broken up by the weight. Should the difference between pressure inside the cavity and the atmospheric pressure have exceeded the predetermined value fracture will also result.